Inertial effects of hypoelastic cylindrical bar of grade zero under simple extension of constant velocity

In this paper an analytical solution for finite deformation at the simple extension of a hypoelastic cylindrical bar of grade zero under constant velocity is obtained. It is found that the difference between stress-strain curves at different tensile velocities is only due to the inertial terms in the solution. The axial stress due to inertia increases with the square of ratio of tensile velocities.     

二极管侧泵浦板条固体激光器的热效应研究

 用有限差分法对二极管侧泵浦板条激光介质的温度分布作了数值计算。在此基础上, 对不同条件下二极管侧泵浦激光器的最佳冷却方案进行了研究。用峰值功率为100W, 工作频率为100Hz的二极管泵浦Nd:YAG板条作了实验研究, 所得结果与计算符合较好。     

Finding the efficiency score and RTS characteristic of DMUs by means of identifying the efficient frontier in DEA

Data envelopment analysis (DEA) is basically a linear programming based technique used for measuring the relative performance of organizational units, referred to as decision-making units (DMUs), where the presence of multiple inputs and outputs makes comparisons difficult. The ability of identifying frontier DMUs prior to the DEA calculation is of extreme importance to an effective and efficient DEA computation. In this paper, a method for identifying the efficient frontier is introduced. Then, the efficiency score and returns to scale (RTS) characteristic of DMUs will be produced by means of the equation of efficient frontier.     

非线性纵向数据模型中自相关性和随机效应的存在性检验

刻画纵向数据协方差结构有三种可能因素 ,即序列相关 (特别是一阶自相关 )、随机效应和常规的随机误差 (Diggleetal,2 0 0 2 ) .本文研究非线性纵向数据模型的自相关性和随机效应存在性的单个和联合检验 ,得到了检验的score统计量 ,并利用血浆药物渗透数据 (Davidian&Gilinan ,1 995)说明检验方法的应用 .     

Thermodynamics of the two-dimensional O(3) σ-model with fixed-point lattice action

The free energy density of the two-dimensional O(3) non-linear σ-model is calculated at finite temperature and finite spatial extent. Both an analytic calculation in the perturbative regime and a Monte Carlo study at low temperatures are presented. It is shown that using the fixed-point action instead of the standard Wilson action leads to a substantial reduction of the cut-off effects.     

The modified k·p method to investigate polarization effects in nitride quantum-well devices

The modified k·p method (which includes both stress and polarization effects) has been used to investigate recombination phenomena in nitride quantum-well (QW) devices. Within their volumes, both spontaneous and piezoelectric polarization have been found to have an essential influence on carriers behaviour. In particular, as a result of the quantum-confined Stark effect, energy of radiation emitted within the AlGaN/GaN/AlGaN QW has been found to decrease rapidly with an increase in the AlN mole fraction of the barrier material, which means—with an increase in mechanical stresses at the GaN/AlGaN heterojunctions. It should also be stressed that screening of polarization effects induced by free carriers at least partly reduced the above stress influence. So both effects, polarization and its screening, are equally important in exact modelling of an operation of nitride QW devices.     

Effects of relativistic motion of electrons on the chemistry of gold and platinum

Experimental evidence proving the unique stabilization of the 6s orbital in platinum and gold is presented. The conclusions are drawn from the chemical reactivities, of both elements, as well as from structural and spectroscopic features of selected compounds. In particular, the opening of a band gap in transparent CsAu and Cs₂Pt, backed by band structure calculations, are regarded conclusive indications of Au⁻ and Pt²⁻ to exist as closed shell species in these compounds.     

Controlling influences in bisspiroketal formation: synthesis of the ABC ring system of azaspiracid

Substitution effects on the stereochemical outcome of bisspiroketalization on the C₁-C₁₇ carbon backbone of azaspiracid is presented. A possible explanation is offered to explain the observed stereochemical outcome.     

Thermodynamics of wurtzite GaN from first-principle calculation

The density function perturbation theory (DFPT) is employed to study the linear thermal expansion and heat capacity at constant pressure (with the quasiharmonic approximation) for wurtzite GaN. The calculated results of linear thermal expansion coefficient and heat capacity at constant pressure are compared with the available experimental data in a wide temperature range. Generally these properties calculated agree well with experimental data except at high temperature, thus it suggests the thermal expansion and heat capacity can be well calculated from this first-principle approach.     

Optimum convective heat transfer coefficient for diode-pumped laser slabs

It is important for laser designers to study the characteristics of heat transfer from the laser crystal slab to the coolant in high-power DPSS laser operations. We have simulated and obtained the optimum heat transfer coefficient and coolant flow rate for our cavity design, in which the circulating coolant is maintained at a constant temperature. It has been determined that the coolant temperature and the convective heat transfer coefficient (h) are important parameters in the thermal analysis. The coefficient h is affected by the coolant flow rate, the physical properties of the laser slab and the coolant and the pumping cavity geometry. Using analytical heat transfer equation, for cooling water temperature of 300 K, the optimum flow rate for our cavity geometry is found to be 390 cm³/s, corresponding to h=5 W/cm² K.